Sparkless camera shutter and flash tube synchronizer



Jan. 16, 1951 c, w. MGCARTY 2,538,577

SPARKLESS CAMERA SHUTTER AND FLASH TUBE SYNCHRONIZER Filed May 8, 1948Invervh'or" Ctgde W. M CaT- c5,

Patented Jan. 16 1951 "UNITED STATES PA E T OFFICE srAnKI JEss CAMERASHUTTER. AND FLASH I TUBE SYNCHB-ONIZER Clyde W. McCarty, Lynn, Mass,assignortoGeneral Electric Company, a corporation of New YorkApplication May 8, 1948, Serial No. 25,863

V 1 Claim. (Cl. 95-11.5)

This invention relatesto electric discharge dethrough the enclosed gas.However, ionization vices and more particularly to -a new and immay beincreased sufficiently to cause discharge proved apparatus fortriggering so-called flash by' sharply increasing the voltage gradientin the @1 v gas, or a portion thereof. Such a voltage gradientHeretofore, there have been devised various 5 increase causes increasedionization since diseiici'tation circuits for controlling theconductivity placement current or condenser charging current of cashlamps. However, these circuits, emin the dielectric consisting of theenclosed gas bodyi'ng switches which employ current-carrying results,whichcurrent causes additional ionizacoiit'acts, could not be used in anexplosive attion. This may be accomplished by applying a niosphere, suchas exists in a hospital operating voltage pulse between anode 3 andcathode 2. room, for instance. Thus, a sparkless apparatus Discharge inlamp I continues as long as the fortriggering'a'flash lamp is needed forapplianode-toecathode'voltage exceeds a critical value cations of thisnature. below .which current flow stops. Thus, asource Anobj'ect of myinvention is to provide a new of anode-to-cathode voltage capable ofsupplying and improved igniterexcitationapparatus for. an energyrandofsharply drooping load characteriselectric discharge device. tic, must beprovided if, flashes of short duration i Another object of my inventionis to provide are desired. Furthen'a large triggering voltage a new andimproved sparkless apparatus for trigmust be suppliedflat the instantillumination is gering a photographicgfiash lamp of the gaseousde'sirednu conduction type. I 0 In accordancerwith my invention, lamp Iis A further object of myinvention is to provide connected across adischarge circuit 5, 5' which a. new aridimproved apparatus fortriggering a may be energized from a 118 volt, 60 cycle source flashl'amp, which apparatus employs amagnet ofcurrent through the primarywinding 6 of a secured'to ashutter' of 'a' camera'for actuatingtransformer l. A manual make-and-break cona control valve which in turntriggers the flash trol switch 8 maybe used to connect transformer lamp.1 I to the source of current. A secondary winding Further features andadvantages of my inven- 9 of transformer I is connected through arectition will appear from the following description fier I0, and acharging impedance II which may of species thereof. be constituted ofinductance or resistance, or

For a better understanding of my invention 30 both, to a capacitance l2.A rectified or direct reference may be had to the followingdescriptioncurrent source is thus provided for charging the taken in connectionwith the accompanying drawcapacitance I2 to a voltage, for example, of2000 ing and its scope will be pointed out in the apvolts. A bleederresistance I3 is connected across pended claim. The drawing is adiagrammatic capacitance I2, which in turn is in parallel with view ofan electric discharge device and a triggerlamp l. A control valve ortrigger tube I4 may be ing device therefor incorporating my invention.connected to terminals I5 and I6 of the bleeder Referring to thedrawing, I have there il1us= resistance I3, so as to be supplied with adesirable trated one embodiment of my invention as-applied operatingvoltage therefrom. The trigger tube I4 to an electric discharge lamp I.Lamp I may be may be a thyratron which may comprise an of the coldcathode gas or mercury vapor type evacuated glass envelope II- filledwith a suitable which has come into general use, particularly in gas,such as neon, and is provided with a plurality photographicapplications, mainly because of its of electrodes, namely a cathode I8,an anode or ability to emit high intensity illumination and plate I9, acontrol grid 20, and. a shield grid 2I. to reach full intensity almostinstantaneously. To terminals I5 and I6 of bleeder I3 there is Inaddition, lamp I is usually designed to furnish als connected, in seriest a capacitance a illumination only during very short increments p yWinding 3 Of a voltage transformer 24. of time and to furnish such aflash at any chosen A secondary winding 25 of transformer 24 isconinstant and at any chosen repetition rate. nected o a triggering coil26 Wound around en- Lamp I usually comprises a cathode 2 and a velope 4of lamp I. Control grid 20 is connected anode 3 within a gas-tightvitreous envelope 4 through a resistance 21 to a wire coil 28. Acontaining a suitable gas such as xenon or argon magnet 29 which, forexample, may be a bar or mercury in liquid or vapor form. Electricalmagnet three-eighths of an inch indiameter, discharge does not occurwhen normal anode-tomounted on a flap or door type shutter 30 of acathode voltage is applied, since ionization re- 5 ca e a 3 s Provided oat e er mains sufiiciently low to prevent breakdown tube I4 upon openingof the camera shutter 30.

the trigger tube Coil 28 is mounted in the path of movement of magnet 29so that upon opening of shutter 30 of camera 3! the magnet will moveinto coil 28 which is located near the end of travel of magnet 29.Magnet 29 in turn induces a voltage impulse in coil 29 which issufficient to cause the tri er tube or thyratron I 4 to fire, thethyratron grid voltage being 'adjusted'so that the voltage generated incoil 28 by magnet-29 is sufficient to cause tube [4 to conduct. Thecondenser 22 then discharges through the condenser discharge circuitcomprising the trigger tube l4 and the primary winding 23 of transformer24. The resulting high-voltage surge of the secondary winding 25 oftransformer 24 is applied to the triggering coil 26 which is woundaround the envelope 4 of lamp I. This causes the gas in the lamp I toionize, permitting the condenser I2 to discharge through lamp I betweenits electrodes, producing a very brilliant flash of short duration.

Thus, when the entire installation is energized by closing switchS,condenser I2 becomes charged from the direct current source supplied bythe rectifier tube 52, trigger tube M being non-conductive. The sourceof direct current in addition charges'the condenser 22 at the same time.Any time aiter'the voltage across'condens'ers l2 and22 has reached itsmaximum value, the shutter 3a of camera 31 may be opened and an inducedvoltage is generated in coil 28 by the action of magnet 29 entering intocoil 28. This induced voltage in coil 23 raises the potential of thecontrol grid 2-0 until the breakdown voltage between control grid Ziland cathode I3 is exceeded and M becomes conductive. condenser 22, asheretofore mentioned, then discharges th'rough the condenser-dischargecircuit comprising trigger tube It and the primary winding 23 oftransformer 24!. The resulting highvcitage surge of the secondarywinding 25 or a transformer 24 is applied to the triggering coil 26 oflamp I. This causes the gas in lamp I to ionize, permitting thecondenser I2 to discharge through the lamp I, and thus produce a verybrilliant flash of short duration. When the con- The I denser I2 isfully discharged, the discharge lamp I promptly extinguishes and thecycle is ready for repetiton.

When the condenser I2 is fully discharged the voltage across the bleederI3 is approximately zero and thus prevents condenser 22 from chargingand, in turn, permits trigger tube [4 to de-' ionize. The time taken fora complete cycle of operation is very brief and the apparatus is againready for a repetition cycle.

What I claim as new and desire to secure by Letters-Patent of the UnitedStates is:

In combination with a gaseous electric discharge lamp having a pluralityof electrodes therein, a "current supply circuit, a discharge circuitconnected to said electrodes across said supply circuit to effect aflash-producing discharge through said lamp, a starting circuit forsupplying a triggering voltage to said lamp at a point on said lampintermediate said electrodes and comprising a voltage step-up means anda grid controlled electricvalve control means connected to controlcurrent flow through said step-up means, a camera, a normally closedflap type shutter mounted on said camera, a magnet mounted on saidshutter, and a wire induction coil mounted in the path of movement ofsaid magnet near the end of the path of travel thereof and connected tosupply a potential to the grid of said control means sufiicient torender the control means conductive and permit current flow through saidstep-up means.

CLYDE W. McCARTY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,299,497 Rosenthal Oct. 20, 1942 2,358,796 Edgerton Sept. 26, 1944 2,408,764 Edgerton Oct. 8, 1946

